1404. Cook, R.J.. 1990 Jan.. Rotation effects and plant disease.. presentation at STEEP Annual Review, Moscow, ID.In monocrop wheat, the average fumigation response is 70%. It drops to about 20% in a 2-year rotation (W-P) and to about 7% in the 3 year rotation (W-B-P). There is a 3-way complex of major disease organisms in our dryland cropping - Take-all, Pythium, and Rhizoctonia. Rhizoc. and Take-all are more severe in the drier areas. Pythium is more of a problem in the more acid, higher clay soils. Peas and lentils are good hosts for Rhizoc., yet wheat after peas is healthier. There is less plant material residue to act as a host for Rhizoc. after peas compared to after wheat. At Lind, WA, take-all decline did not occur with no-till. Once take-all decline set in, then the incidence of Rhizoc. increased. With rotation, you often don't need the tillage to help control disease. There has been a debate whether these diseases come from the soil or from the straw. Recent experiments found that the soil hosted the organisms, but the residue in the soil was an important food source. There was no effect on crop growth when straw from a previous crop was fumigated. In another test, there was no benefit from a paired-row configuration, either with fumigation or with a good rotation. Uniform row spacing is best when there is a higher risk for disease.

8384. Beus, C., D. Dillman, and J. Carlson. 1990. Palouse agriculture: a survey on production practices, policies, and problems.. unpublished results, Dept. of Rural Sociology, Washington St. Univ., Pullman, WA 99164.This random survey was done in the Palouse area of eastern WA and northern ID, with a random sample of about 260 farmers. Average farm size was 1392 acres. One-third of the respondents would like to change their current rotation, primarily to reduce disease problems, but consider government programs to be the biggest barrier. Desire to use no-till planting was evenly split. Half the respondents felt they were using most of the available erosion control practices. Large percentages (>60%) felt that contour tillage, surface roughness, no-till, good plant cover, and tilth were very important erosion control factors. Herbicide and fertilizer use trends over the past five years were normally distributed. Use of fungicides on wheat (other than seed treatment) was generally less than 20%. Half the farmers currently use soil testing, and of those, 90% tested for residual N to 4-5 ft. depth. Half the respondents felt they had cut back on pesticide and fertilizer use since their high point, while only 10-20% felt they would do so in the future. About 65% had heard of the LISA program, and 26% indicated opposition to it.

10988. Cook, R.J.. 1981. The influence of rotation crops on Take-all decline phenomenon.. Phytopathology 71:189-192.Five rotation crops (potatoes, oats, alfalfa, beans, grass) were tested for their ability to promote take-all decline in continuous wheat. Take-all from natural inoculum was common on wheat plants in plots previously planted to wheat, grass, or soybeans, but was mild or nonexistent on wheat after oats, potatoes, or alfalfa. When inoculum was introduced, take-all was severe in plots previously planted to potatoes, oats, alfalfa, or beans, whether or not the soil had been fumigated. In contrast, soil in plots previously planted to wheat or the grass mixture had to be fumigated before disease of such severity could develop in response to introduced inoculum. Soils cropped continuously to wheat or wheat in rotation with grass were suppresive to take-all; the other crops resulted in soil becoming highly conducive to take-all.